1. Field of the Invention
The present invention relates to an automatic focus adjustment device for a photographic camera, video camera, or the like.
2. Description of Related Art
The related art technology is described hereafter, with reference to FIG. 1. FIG. 1 shows the continuous photography sequence of a camera with which continuous photography is possible. An autofocus (AF) accumulation calculation, the states of and object positions (solid line 20) for an AF motor, SQ motor, and feeding motor, and the lens positions (dash line 21) are shown. .quadrature.(an empty box) shows the AF accumulation. Shorter elongated darkened boxes 22 indicate exposures and a longer elongated darkened box (not numbered) shows the AF calculation. The CCD accumulation begins after a specified time interval has elapsed after the mirror down operation. After the CCD accumulation is finished, the focus detection calculation is accomplished. The AF motor is used to drive the lens, and has a driving state and a stopped state. The SQ motor is a motor that controls the mirror up operation, diaphragm regulation, the mirror down operation, and shutter operation of the camera. When this motor rotates in the forward direction, the mirror up and diaphragm closing operations are accomplished; in the reverse rotation direction, the mirror down, diaphragm reset, and shutter operations are accomplished. The feeding motor is a motor that accomplishes film feeding. For continuous photography second frame lens driving of a conventional camera, lens driving is permitted and is accomplished based on the focus detection calculation when the focus detection calculation is finished after mirror down and when either the SQ motor or the feeding motor is stopped.
With a camera that accomplishes high-speed continuous photography, when continuous photography is accomplished for a moving object, the time interval for the mirror up operation is approximately the time interval during which lens driving is possible. The mirror up time interval is generally 50 ms to 100 ms, and becomes shorter if the frame speed during continuous photography is increased. Therefore, the exposures (shown by short darkened boxes 22 in FIG. 1) are accomplished before the lens driving that must occur between frames has been completed, and an out-of-focus picture is taken. In the case of a system in which exposure is accomplished after waiting for the lens driving to finish, the frame speed must necessarily be decreased.